It is probable, because of low visibility in fog and light drizzle, that the pilot made a navigational error and inadvertently entered the valley to the north rather than turning to the east toward Sewell Inlet. The aircraft heading at impact, 150 degrees off the required heading, indicates that the pilot had turned the aircraft around. This reversal of course could have been made because the pilot recognized that he was in the wrong valley or because he began to encounter adverse weather conditions. Because the aircraft struck the terrain in a wings-level attitude, indicating no last-second evasive manoeuvring by the pilot, it is likely that the pilot's forward visibility was restricted and that he did not see the ground in time to avoid impact. If the weather observed by the witness, 4 nm south of the accident site, had prevailed in the valley at the time of the accident, it is likely that the aircraft would have entered the clouds prior to it reaching the crash elevation of 1,700 feet. Once the aircraft was in cloud, the pilot would have had no other option than to climb to avoid the high terrain. It is probable that the pilot delayed his decision to reverse course until he was unable to avoid the weather.Analysis It is probable, because of low visibility in fog and light drizzle, that the pilot made a navigational error and inadvertently entered the valley to the north rather than turning to the east toward Sewell Inlet. The aircraft heading at impact, 150 degrees off the required heading, indicates that the pilot had turned the aircraft around. This reversal of course could have been made because the pilot recognized that he was in the wrong valley or because he began to encounter adverse weather conditions. Because the aircraft struck the terrain in a wings-level attitude, indicating no last-second evasive manoeuvring by the pilot, it is likely that the pilot's forward visibility was restricted and that he did not see the ground in time to avoid impact. If the weather observed by the witness, 4 nm south of the accident site, had prevailed in the valley at the time of the accident, it is likely that the aircraft would have entered the clouds prior to it reaching the crash elevation of 1,700 feet. Once the aircraft was in cloud, the pilot would have had no other option than to climb to avoid the high terrain. It is probable that the pilot delayed his decision to reverse course until he was unable to avoid the weather. The aircraft was certified, equipped, and maintained in accordance with existing regulations and approved procedures. The aircraft weight and centre of gravity were within the prescribed limits. No pre-crash airframe failure or engine defect was found. The pilot was certified, trained, and qualified for the flight in accordance with existing regulations. The pilot probably made a navigational error because of restricted visibility in fog and light drizzle and inadvertently entered the valley toward the north. The pilot reversed course because he recognized that he was in the wrong valley or because he began to encounter adverse weather conditions. It is probable that the pilotdelayed his decision to reverse course until he was unable to avoid the weather. It is probable that the pilot entered cloud and did not see the ground in time to take evasive action.Findings The aircraft was certified, equipped, and maintained in accordance with existing regulations and approved procedures. The aircraft weight and centre of gravity were within the prescribed limits. No pre-crash airframe failure or engine defect was found. The pilot was certified, trained, and qualified for the flight in accordance with existing regulations. The pilot probably made a navigational error because of restricted visibility in fog and light drizzle and inadvertently entered the valley toward the north. The pilot reversed course because he recognized that he was in the wrong valley or because he began to encounter adverse weather conditions. It is probable that the pilotdelayed his decision to reverse course until he was unable to avoid the weather. It is probable that the pilot entered cloud and did not see the ground in time to take evasive action. The pilot probably made a navigational error because of restricted visibility in fog and light drizzle and entered the wrong valley, and he delayed his decision to reverse course until he was unable to avoid the weather.Causes and Contributing Factors The pilot probably made a navigational error because of restricted visibility in fog and light drizzle and entered the wrong valley, and he delayed his decision to reverse course until he was unable to avoid the weather.